Lieberman stresses that border closure isn’t a policy that he and other Senators recommend now. “It just seems to us that if we get to a point where contagion can be carried by proximity and there are more of the cases in Mexico, then we want to keep separate for a while.”

Napolitano said in a briefing Thursday, “Closing the entire border would have no benefit at this point because the virus is already in the United States.”

She maintains that “the real focus needs to be now on what do we do to reduce the spread of the disease within our borders. But closing the borders, in and of themselves, won’t have that kind of an impact.”

President Obama Wednesday said closing the border now would be like “closing the barn door after the horses are out.”

Lieberman acknowledges that closing the border would be very disruptive.

“If you close the border with Mexico even temporarily, it would have tremendous economic, dislocating effects,” he says.

“It'll also dislocate a lot of personal lives of people who go back and forth most every day.”

But if closing the border will save lives in the U.S., “then that's a choice that we've got to make,” Lieberman says.